Brainstem (Pons) Injury Can Cause Both Double Vision and Urinary Hesitation
Injury to the pons—the region of the brainstem—can produce both diplopia (double vision) and urinary dysfunction including hesitation. This occurs because the pons contains both the nuclei for cranial nerves controlling eye movements (CN VI, VII) and serves as a critical relay center for bladder control pathways.
Anatomical Basis
The pons houses multiple structures relevant to both symptoms:
Eye Movement Control
- Abducens nucleus (CN VI) originates in the pons and controls lateral eye movement 1, 2
- Pontine lesions frequently affect CN VI, causing horizontal diplopia that worsens at distance and with lateral gaze 3
- The facial nerve (CN VII) curves over the sixth nerve nucleus, so pontine lesions often produce combined CN VI and CN VII palsies 3
- Abnormalities in the rostral pons result in contralateral hypotropia and head tilt 3
Bladder Control Pathways
- The pons contains the pontine micturition center, which coordinates bladder emptying 4
- Infrapontine/suprasacral lesions commonly cause urinary hesitancy (present in 80% of such cases) 5
- An infarct in the pons can lead to incontinence and voiding dysfunction 4
Clinical Presentation Pattern
When the pons is injured, expect:
Ocular findings:
- Horizontal diplopia, worse at distance
- Esotropia (inward eye deviation)
- Abduction deficit on the affected side
- Possible facial weakness if CN VII nucleus involved 3
Urinary findings:
- Hesitancy and difficulty initiating urination
- Urgency and frequency
- Possible urinary retention
- Detrusor-sphincter dyssynergia (38% of cases with neurogenic bladder) 5
Associated Red Flags
Look for additional pontine syndrome features that confirm brainstem localization:
- Contralateral hemiparesis (from corticospinal tract involvement) 3
- Facial numbness (CN V involvement) 1
- Ataxia or coordination problems
- Nystagmus 3
- Sensory deficits
Diagnostic Approach
Immediate imaging: MRI of the brain without and with contrast is the preferred modality 1, 2. In acute settings where stroke is suspected, follow cerebrovascular disease protocols—noncontrast CT can screen for hemorrhage but has limited sensitivity for small pontine infarcts due to beam hardening artifact 1.
Urodynamic considerations: If urinary symptoms persist, urodynamic testing may reveal detrusor overactivity, detrusor-sphincter dyssynergia, or uninhibited sphincter relaxation—all consistent with infrapontine lesions 5.
Important Caveats
Frontal lobe lesions can also cause urinary symptoms (urgency, incontinence) but typically do NOT cause diplopia 6, 7, 8. The frontal micturition center controls voluntary bladder control, and frontal injuries cause incontinence rather than hesitancy.
Multiaxial involvement: In 28% of neurological patients with unexpected urinary symptoms, multiple levels of the nervous system may be affected simultaneously 5. Don't assume a single lesion explains everything.
Vascular etiology: Pontine strokes are the most frequent cause of acute brainstem syndromes 1. In older patients with vascular risk factors (diabetes, hypertension), microvascular ischemia is the leading cause of isolated CN VI palsy 3.
The combination of diplopia and urinary hesitation strongly suggests pontine pathology and warrants urgent neuroimaging to identify ischemic, hemorrhagic, demyelinating, or mass lesions affecting this critical brainstem region.